(1) Field of the Invention
The present invention relates to a switching power supply circuit which, as a non-insulated power supply circuit that stabilizes DC output voltage, stabilizes output voltage using a three-terminal switching regulator.
(2) Description of the Related Art
Conventionally, switching power supply circuits have been widely used which, by using a three-terminal switching regulator, stabilize output voltage as non-insulated power supply circuits that stabilize DC output voltage in power supply circuits incorporated in electronic devices, for example.
A conventional switching power supply circuit provides feedback of output voltage using a transmission circuit having insulated input and output like a photocoupler as a transmission circuit transmitting a signal corresponding to output voltage to a controller that controls switching operations (see, for example, FIG. 6 of Patent Reference 1: U.S. Pat. No. 6,294,903 (FIGS. 5 and 6)).